1. Field of the Invention
The present invention relates generally to measurement systems and methods, and more particularly to a system and an associated method for making time-of-flight non-contact optical measurements of the velocity and acceleration of objects.
2. Description of the Prior Art
In the prior art, many applications require knowledge of the speed (i.e., linear and/or rotational velocity) and acceleration of an object that is traveling in a specified direction at one or more points along its path of motion. This occurs, for example, in the case of an object moving on an assembly line or in the case of a cylindrical object that moves along its longitudinal axis in a tube or is launched through such a tube.
Various methods for the measurement of velocity and acceleration of an object with respect to a reference system exist. One measuring method described in the prior art includes the use of inertial sensors such as accelerometers and gyroscopes which are attached to the object of interest to measure the object's linear and rotary acceleration, and thereby velocity and position. Another measuring method described in the prior art includes lasers or radar type devices, which are directed towards the object and based on the returned signal, the position, and thereby the velocity and acceleration of the object is determined. When the object has only one degree-of-freedom with respect to the reference system, such as the rotation of a shaft relative to its bearing (a rotary joint), or the sliding of a block in a linear guide-way such as a linear bearing (prismatic joint), optical encoders are very often used to measure the relative motion at the joint, i.e., the angular rotation of the shaft relative to its bearing support or the linear motion of the block relative to its guide-way. Other measuring methods, which are similar to and more sophisticated than those described hereinabove, such as laser interferometry, have also been developed for the aforementioned purposes. All existing prior art approaches, however, suffer from one or more of the following disadvantages: (1) a number of such devices can only measure linear velocity and/or acceleration. In some cases, however, such as for the case of accelerometers, one may employ a plurality of devices and thereby measure rotational acceleration; (2) many of these devices, for example accelerometers and gyroscopes, have to be mounted on the object together with all the required electronics and power sources. In many cases, this may not be feasible due to space or weight considerations, or may not be economical to mount such relatively expensive devices on the object; (3) the measuring sensors and their related instrumentations that have to be mounted on or within the object may interfere with the operation of the object; (4) it is very difficult to retrofit objects with devices that have to be mounted on or within the object; (5) sensors such as accelerometers and gyroscopes do not provide information about the initial object position and orientation and their related velocities relative to a reference system and the fixed coordinate system. This information is necessary in order to integrate the acceleration information to obtain the motion trajectory for the object.
The system and associated methods in accordance with the preferred embodiment of the present invention overcomes the disadvantages associated with those of the prior art.